North Carolina State University researchers along with researchers from the Russian Academy of Sciences conducted research on two dozen American cockroaches to understand the antennae-cleaning behavior of insects. It was found that the cockroaches and other insects groom to increase their sense of smell.
To conduct the study, researchers disrupted the grooming of some of the roaches so that they could compare the results of groomed antennae against the ungroomed antennae of the roaches. Several methods imaginable were used to keep the roaches from grooming. The methods included using a small plastic clip to anchor the antennae, gluing the roaches' mouths shut, or restricting the roaches' grooming space by placing it in a confined box.
After a 24 hour observation, the tethered antennae of the roaches became shiny compared to the non-tethered antennae. Upon further inspection under a scanning electron microscope, an unidentified substance was found on the antennae. The substance coated the roaches' antennae and blocked the sensory pores. "The insect antennae is full of sensory structures, called sensilla, used by insects to gather information about their surroundings, which is essential for their survival," said Dr Katalin Boroczky from the North Carolina State University, US, who authored the study.
Samples of the substance were analyzed by separating the components of it, using gas chromatography. Although the research was conducted in a sterile environment, stearic acid from the roaches' containers and geranyl acetate from the air were found to collect on the antenna. The roaches secrete a natural substance made up of fatty molecules to help regulate water loss. The researchers thought that the buildup impaired the roaches' ability to smell, as the antennae serve as the insect's nose. "We conclude that the disruption of grooming interferes with general olfaction," the authors wrote in their paper.
By exposing both groomed and ungroomed antennae roaches to sex pheromones, the theory was tested. The roaches with the clean antennae were proven to be much more receptive than the roaches with the dirty antennae. The study was repeated on other insects including houseflies, carpenter ants and German cockroaches and the researchers found that the same buildup on antennae occurred. "Our observations with four phylogenetically diverse species indicate that this hitherto unknown role for grooming is common to a wide diversity of insects," they concluded.
